Lte system signaling procedures

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Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Security Level: Internal Use
LTE system signaling
procedure
2010-09

 Upon completion of this course, you will be able to ：
 Know the LTE/SAE system architecture and functions
 Know main elementary procedures of S1/X2/Uu interfaces
 Know the procedure of service setup, service release, intra-
eUTRAN handover
Page2
Objectives

Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved. Page3
 3GPP TS 36.300
 3GPP TS 23.401
 3GPP TS 36.413
 3GPP TS 36.331
 3GPP TS 36.423
References

1. Overview
2. Elementary Procedures
3. Service signaling flow
Contents

1. Overview
Contents

 Main functions of the Serving GW is:
 the local Mobility Anchor point for handover (inter-eNodeB/inter-3GPP)
 Packet routeing and forwarding
 Main functions of the PDN GW is:
 UE IP address allocation
 UL and DL service level charging
SGi
S12
S3
S1-MME
PCRF
Gx
S6a
HSS
Operator's IP
Services
(e.g. IMS, PSS etc.)
Rx
S10
UE
SGSN
LTE-Uu
E-UTRAN
MME
S11
S5Serving
Gateway
PDN
Gateway
S1-U
S4
UTRAN
GERAN
Page6
System Architecture Overview

 A radio bearer transports the packets of an EPS bearer between a UE and an
eNB. There is a one-to-one mapping between an EPS bearer and a radio
bearer.
 An S1 bearer transports the packets of an EPS bearer between an eNodeB
and a Serving GW
 An eNB stores a one-to-one mapping between a radio bearer and an S1 to
create the binding between a radio bearer and an S1 bearer in both the
uplink and downlink.
Page7
Bearer service architecture

Service request procedure
Page8

 Basically, bearers can be classified into two categories
 GBR bearers
 Non-GBR bearers
 Each bearer has an associated QoS Class Identifier (QCI), and an Allocation
and Retention Priority (ARP)
 QoS Class Identifier (QCI)
 QCI is characterized by priority, packet delay budget and acceptable packet loss rate
 QCI is used to control bearer level packet forwarding treatment
 The set of standardized QCIs is listed in the table of next page
 The ARP of a bearer is used for call admission control
 A GBR bearer is additionally associated with the following bearer level QoS
parameters:
 Guaranteed Bit Rate (GBR)
 Maximum Bit Rate (MBR)
Page9
Bearer level QoS

 The set of standardized QCIs
Page10
Bearer level QoS(Cont.)

Application protocol identities
 EPS bearer identity
 An EPS bearer identity uniquely identifies an EPS bearer for one UE accessing via E-UTRAN
 The EPS Bearer Identity is allocated by the MME
 There is one to one mapping between EPS RB and EPS Bearer, and the mapping between
EPS RB Identity and EPS Bearer Identity is made by E-UTRAN
 eNB UE S1AP ID
 A eNB UE S1AP ID shall be allocated so as to uniquely identify the UE over the S1 interface
within an eNB
 MME UE S1AP ID
 A MME UE S1AP ID shall be allocated so as to uniquely identify the UE over the S1
interface within the MME
 Old eNB UE X2AP ID
 An Old eNB UE X2AP ID shall be allocated so as to uniquely identify the UE over the X2
interface within a source eNB
 New eNB UE X2AP ID
 An New eNB UE X2AP ID shall be allocated so as to uniquely identify the UE over the X2
interface within a target eNB
 C-RNTI: The C-RNTI provides a unique UE identification at the cell level identifying
RRC Connection and used for scheduling
Page11

1. Overview
Contents

2.1 Elementary Procures of Uu
2.2 Elementary Procedures of S1
2.3 Elementary Procures of X2
Contents

UE states
 RRC_IDLE
 A UE specific DRX may be configured by upper layers
 UE controlled mobility
 The UE:
 Monitors a Paging channel to detect incoming calls;
 Performs neighbouring cell measurements and cell (re-)selection;
 Acquires system information.
 RRC_CONNECTED
 Transfer of unicast data to/from UE.
 At lower layers, the UE may be configured with a UE specific DRX.
 Network controlled mobility
 The UE:
 Monitors control channels associated with the shared data channel to determine if
data is scheduled for it;
 Provides channel quality and feedback information;
 Performs neighbouring cell measurements and measurement reporting;
 Acquires system information
Page14

Signalling radio bearers
 "Signalling Radio Bearers" (SRBs) are defined as Radio Bearers (RB) that are
used only for the transmission of RRC and NAS messages. the following
three SRBs are defined:
 SRB0 is for RRC messages using the CCCH logical channel;
 SRB1 is for RRC messages as well as for NAS messages prior to the
establishment of SRB2, all using DCCH logical channel;
 SRB2 is for NAS messages, using DCCH logical channel. SRB2 has a lower-
priority than SRB1 and is always configured by E-UTRAN after security
activation
Page15

System information
 System information is divided into the MasterInformationBlock (MIB) and a
number of SystemInformationBlocks (SIBs).
 The MIB includes a limited number of most essential and most frequently
transmitted parameters that are needed to acquire other information from
the cell, and is transmitted on BCH
 SystemInformationBlockType1 and all SI messages are transmitted on DL-
SCH
E-UTRAN
MasterInformationBlock
UE
SystemInformationBlockType1
SystemInformation
Page16

Paging
 Purpose:
 To transmit paging information to a UE in RRC_IDLE and/ or to inform UEs in
RRC_IDLE and UEs in RRC_CONNECTED about a system information change or
about an ETWS (Earthquake and Tsunami Warning System ) primary notification
 Main IE:
 ue-Identity
 cn-Domain
 pagingCause
 systemInfoModification
 ETWS notification
Paging
UE EUTRAN
Page17

RRC connection establishment
 Purpose:
 RRC connection establishment involves SRB1 establishment. The procedure is
also used to transfer the initial NAS dedicated information/ message from the
UE to E-UTRAN
 Main IE:
 establishmentCause
 radioResourceConfiguration for Only SRB1
 selectedPLMN-Identity
 registeredMME
 nas-DedicatedInformation
RRCConnectionSetup
RRCConnectionRequest
UE EUTRAN
RRCConnectionSetupComplete RRCConnectionReject
RRCConnectionRequest
UE EUTRAN
Page18

Initial security activation
 Purpose:
 To activate AS security upon RRC connection establishment
 When only SRB1 is established and prior to establishment of SRB2 and/ or DRBs.
 Main IE:
 integrity protection and ciphering
SecurityModeComplete
SecurityModeCommand
UE EUTRAN
SecurityModeFailure
SecurityModeCommand
UE EUTRAN
Page19

RRC connection reconfiguration
 Purpose:
 To modify an RRC connection, e.g. to establish/ modify/ release RBs, to perform
handover, to setup/ modify/ release measurements
 Main IE:
 measurementConfiguration
 mobilityControlInformation
 nas-DedicatedInformation
 radioResourceConfiguration (for SRB2 and possibly DRBs)
 securityConfiguration
 ue-RelatedInformation
RRCConnectionReconfigurationComplete
RRCConnectionReconfiguration
UE EUTRAN
RRC connection re-establishment
UE EUTRAN
Page20

RRC connection release
 Purpose:
 To release the RRC connection, which includes the release of the established
radio bearers as well as all radio resources.
RRCConnectionRelease
UE EUTRAN
Page21

Mobility from E-UTRA
 Purpose:
 To move a UE in RRC_CONNECTED to a cell using another Radio Access
Technology (RAT), e.g. GERAN, UTRA or CDMA2000 systems
 The mobility from E-UTRA procedure covers both:
 handover, i.e. the MobilityFromEUTRACommand message includes radio resources
that have been allocated for the UE in the target cell
 cell change order, i.e. the MobilityFromEUTRACommand message may include
information facilitating access of and/ or connection establishment in the target cell,
e.g. system information. Cell change order is applicable only to GERAN.
MobilityFromEUTRACommand
UE EUTRAN
Page22

DL/UL information transfer
 Purpose:
 To transfer NAS or non-3GPP dedicated information from E-UTRAN/UE to a
UE/E-UTRAN in RRC_CONNECTED
DLInformationTransfer
UE EUTRAN
ULInformationTransfer
UE EUTRAN
Page23

UE capability transfer
 Purpose:
 To transfer UE radio access capability information from the UE to E-UTRAN
UECapabilityInformation
UECapabilityEnquiry
UE EUTRAN
Page24

Contents

Paging
 Purpose:
 The purpose of the Paging procedure is to enable the MME to page a UE in the
specific eNB
 Main information:
 UE Paging ID
 Paging DRX
 Paging Cause
 List of TAIs
PAGING
eNB MME
Page26

Context Management procedures
 Purpose:
 To establish the necessary overall initial UE Context including SAE Bearer context, Security context,
Handover Restriction List, UE capability information, NAS-PDU etc
 Other message in this category includes: UE Context Release Request /release/modify
 Main information:
 SAE Bearer Level QoS parameters
 Transport Layer Address
 NAS-PDU
 Security
 Handover Restriction List
 UE Radio Capability
 Subscriber Profile ID for RAT/Frequency priority
INITIAL CONTEXT SETUP RESPONSE
INITIAL CONTEXT SETUP REQUEST
eNB MME
Page27

SAE Bearer Management procedures
 Purpose:
 To assign resources on Uu and S1 for one or several SAE bearers and to setup corresponding SAE
Radio Bearers for a given UE
 Other message in this category includes: SAE bearer modify and SAE bearer release
 Main information :
 SAE Bearer Level QoS parameters
 Transport Layer Address
 NAS-PDU
 SAE Bearer Setup List
 SAE Bearer Failed to Setup List
SAE BEARER SETUP RESPONSE
SAE BEARER SETUP REQUEST
eNB MME
Page28

NAS transport
 Purpose:
 The purpose of the NAS Transport procedure is to carry UE – MME signalling over the S1
Interface.
 The NAS messages are not interpreted by the eNB
 Besides INITIAL UE MESSAGE, DOWNLINK NAS TRANSPORT and UPLINK NAS
TRANSPORT messages are used for NAS Transport procedure also
 Main IE:
 NAS-PDU
 TAI
 E-UTRAN CGI
 S-TMSI (optional)
 Handover Restriction List in DOWNLINK NAS TRANSPORT (optional)
INITIAL UE MESSAGE
eNB MME
Page29

S1 Setup
 Purpose:
 The purpose of the S1 Setup procedure is to exchange application level data
needed for the eNodeB and MME to interoperate correctly on the S1 interface.
 This procedure shall be the first S1AP procedure triggered after the TNL
association has become operational
 Main IE:
 Global eNB ID
 eNB Name
 Supported TAs of the eNodeB
eNodeB
S1 SETUP REQUEST
MME
S1 SETUP RESPONSE
eNodeB
S1 SETUP REQUEST
MME
S1 SETUP FAILURE
MME Name
Served PLMNs
Served GUMMEIs
Page30

MME/eNodeB Configuration Update
 Purpose:
 The purpose of the MME/ eNB Configuration Update procedure is to update
application level configuration data needed for the eNB and MME to
interoperate correctly on the S1 interface.
 This procedure doesn’t affect existing UE-related contexts
eNB
ENB CONFIGURATION UPDATE
MME
ENB CONFIGURATION UPDATE ACKNOWLEDGE
eNB
ENB CONFIGURATION UPDATE
MME
ENB CONFIGURATION UPDATE FAILURE
eNB
MME CONFIGURATION UPDATE
MME
MME CONFIGURATION UPDATE ACKNOWLEDGE
eNB
MME CONFIGURATION UPDATE
MME
MME CONFIGURATION UPDATE FAILURE
Page31

Contents

Handover Preparation
 Purpose:
 To establish necessary resources in an eNB for an incoming handover
 Main IE:
 Cause
 Target Cell ID and GUMMEI
 SAE Bearer Info
source
eNB
HANDOVER REQUEST
HANDOVER REQUEST ACKNOWLEDGE
target
eNB
source
eNB
HANDOVER REQUEST
HANDOVER PREPARATION FAILURE
target
eNB
Page33

SN Status Transfer
 Purpose:
 To transfer the uplink PDCP-SN and HFN receiver status and the downlink
PDCP-SN and HFN transmitter status from the source to the target eNB during
an X2 handover for each respective SAE bearer for which PDCP SN and HFN
status preservation applies
 Main IE:
 SAE Bearers Subject To Status Transfer List
source
eNB
SN STATUS TRANSFER
target
eNB
Page34

UE Context Release
 Purpose:
 To signal to the source eNB that control plane resources for the handed over
UE context can be released
 Upon reception of the UE CONTEXT RELEASE message, the source eNB can
release radio and control plane related resources associated to the UE context
source
eNB
UE CONTEXT RELEASE
target
eNB
Page35

Load Indication
 Purpose:
 To transfer load and interference co-ordination information between intra-
frequency neighboring eNBs
 Main IE:
 UL Interference Overload Indication
 UL High Interference Indication
 Relative Narrowband Tx Power (RNTP)
eNB1
LOAD INFORMATION
eNB2
Page36

Resource Status Reporting Initiation /Reporting
 Purpose:
 To request the reporting of load measurements to another eNB
 And to report the result of measurements requested by eNB1 using the
Resource Status Reporting Initiation
eNB1 eNB2
RESOURCE STATUS REQUEST
RESOURCE STATUS RESPONSE
eNB1 eNB2
RESOURCE STATUS UPDATE
Page37

X2 Setup
 Purpose:
 To exchange application level data needed for two eNBs to interoperate
correctly over the X2 interface
 Main IE:
 Served Cell Information
 PhyCID and Cell ID (CGI)
 TAC
 Broadcast PLMNs
 UL EARFCN/DL EARFCN and Cell Transmission Bandwidth
eNB1
X2 SETUP REQUEST
eNB2
X2 SETUP RESPONSE
eNB1
X2 SETUP REQUEST
eNB2
BB
X2 SETUP FAILURE
Page38

1. Overview
Contents

UE E-NODEB MME
RRC CONN SETUP REQ
RRC CONN SETUP
RRC CONN SETUP CMP
INITIAL UE MESSAGE
INITIAL UE CONTEXT SETUP REQ
RRC SECURITY MODE CMD
RRC SECURITY MODE CMP
RRC CONN RECFG
RRC CONN RECFG CMP
INITIAL UE CONTEXT SETUP RSP
SAEB SETUP REQ
RRC CONN RECFG
RRC CONN RECFG CMP
SAEB SETUP RSP
直直直直直直直直直直直直直
直直直直直直直直直直直直直直直
PAGING
RRC PAGING
NAS: Service request
eNB S1 signaling connection ID
MME S1 signaling connection ID
Security context
UE capability information
Bearer setup (Qos profile, S-GW TEID)
1. authentication
Uplink data could be sent
eNB S1 signaling connection ID
bearer confirm (eNB TEID)
NAS: Session management request
Downlink data could be sent
Uplink information transfer UPLINK NAS TRANSPORT
NAS: Session management response
SRB2 setup
DRB1 setup
DRB2 setup
2. NAS message (service negotiation)
Page40

Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved. Page 41
RRC CONN SETUP REQ

RRC CONN SETUP

RRC CONN SETUP CMP

Direct transfer message of S1interface
Initial UE Message
eNB
Initial UE Message
eNB UE S1AP ID
NAS-PDU
TAI
E-UTRAN CGI
S-TMSI (O)
CSG Identity (O)
RRC Establishment cause
GUMMEI (O)
MME

Direct transfer message of S1interface

Direct transfer (Authentication & ciphering)
Uu interface trace
S1 interface trace

S1 Initial Context Setup Request
Page 47

S1 Initial Context Setup Request
Page 48

RRC Security Mode Command
Security Mode Command
eNBUE
Security Mode Complete
Security Mode Command
Ciphering Algorithm
Integrity Protection Algorithm
Security Mode Failure

UE capability report
Page 50
UECapabilityInformation
UECapabilityEnquiry
UE EUTRAN

RRC connection reconfiguration
Page 51
RRCConnectionReconfigurationComplete
UE EUTRAN
Used to establish SRB2 and default DRB1.

INITI UE CONTEXT SETUP RSP
Page 52
S-GW
Initial Context Setup Request
eNB MME
Initial Context Setup Response
Modify Bearer
Initial Context Setup Response
MME UE S1AP ID
eNB UE S1AP ID
E-RAB Setup List
- E-RAB ID
- Transport Layer Address
- GTP-TEID
E-RAB Failed to Setup List (O)
Criticality Diagnostics (O)
S-GW Address
and TEID
eNB Address and
TEID
E-RAB ID = 5

INITI UE CONTEXT SETUP RSP
Page 53

Uu interface trace
S1 interface trace

S1 release procedure
 Purpose:
 To release the logical S1-AP signalling connection (over S1-MME) and all S1
bearers (in S1-U) for a UE. The procedure will move the UE from ECM-
CONNECTED to ECM-IDLE in both the UE and MME, and all UE related context
information is deleted in the eNodeB
1. S1-AP: S1 UE Context Release Request
MME
5. RRC Connection Release
UE eNodeB Serving GW
2. Update Bearer Request
3. Update Bearer Response
4. S1-AP: S1 UE Context Release Command
6. S1-AP: S1 UE Context Release Complete
Page55

Intra EUTRAN X2-based handover without
Serving GW relocation
 See notes for details
Handover completion
UE
Source
eNodeB
Serving
GW PDN GWMME
Target
eNodeB
Downlink and uplink data
Forwarding of data
Downlink data
Uplink data
1 Path Switch Request
2 User Plane Update Request
3 User Plane Update Response
5 Path Switch Request Ack
6 Release Resource
Downlink data
4. End marker
4. End marker
7. Tracking Area Update procedure
Handover decision
Measurement report
Handover request
Handover request ack
Handover command
Page56

Intra EUTRAN X2-based handover with
Serving GW relocation
Handover completion
UE
Source
eNodeB
Source
Serving GW PDN GWMME
Target
Serving GW
Target
eNodeB
Handover execution
3a. Update Bearer Request
Downlink and uplink data
Handover preparation
Forwarding of data
Downlink data
Uplink data
1. Path Switch Request
3b. Update Bearer Response
2. Create Bearer Request
4. Create Bearer Response
5. Path Switch Request Ack
6. Release Resource
Downlink data
Uplink data
7a. Delete Bearer Request
7b. Delete Bearer Response
(A)
(B)
Page57

Intra EUTRAN S1-based handover
UE
Source
eNodeB
Source
MME
Source
Serving GW PDN GW
Target
MME
Target Serving
GW
Target
eNodeB
Detach from old cell and
synchronize to new cell
HSS
2. Handover Required
Downlink User Plane data
1. Decision to trigger a
relocation via S1
3. Forward Relocation Request
5. Handover Request
5a HandoverRequest Acknowledge
7. Forward Relocation Response
9. Handover Command
10. Handover Command
11a. Only for Direct forwarding of data
12. Handover Confirm
Downlink data
13. Handover Notify
.
8a. Create Bearer Response
11b. Only for Indirect forwarding of data
Uplink User Plane data
Page58

Intra EUTRAN S1-based handover
UE
Source
eNodeB
Source
MME
Source
Serving GW PDN GW
Target
MME
Target Serving
GW
Target
eNodeB HSS
17. Update Bearer Response
Downlink User Plane data
14. Forward Relocation Complete
14b. Forward Relocation Complete Acknowledge
16a. Update Bearer Response
(A)
19c. Delete Bearer Request
(B)
19a. UE Context Release Command
19b. UE Context Release Complete
19d. Delete Bearer Response
Page59

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